add hw2

node_modules/lodash/isWeakSet.js

@@ -0,0 +1,28 @@
+var baseGetTag = require('./_baseGetTag'),
+    isObjectLike = require('./isObjectLike');
+
+/** `Object#toString` result references. */
+var weakSetTag = '[object WeakSet]';
+
+/**
+ * Checks if `value` is classified as a `WeakSet` object.
+ *
+ * @static
+ * @memberOf _
+ * @since 4.3.0
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is a weak set, else `false`.
+ * @example
+ *
+ * _.isWeakSet(new WeakSet);
+ * // => true
+ *
+ * _.isWeakSet(new Set);
+ * // => false
+ */
+function isWeakSet(value) {
+  return isObjectLike(value) && baseGetTag(value) == weakSetTag;
+}
+
+module.exports = isWeakSet;